bacteria multiply by simple cell division (binary fission) as often as every 20mins if they have enough nutrients + a suitable temperature 

how do bacteria multiply + how often do they multiply

it allows sufficient transport of molecules into + out of the cell to meet the needs of the organism 

why does a single-called organism have a relatively large surface area to volume ratio 

its exchange surface is increased by having a large surface area so exchange can take place faster 

how are the small intestine + lungs in mammals,gillet in fish and roots+shoots in plants adapted for exchanging materials 

- diffusion + active transport involve the movement of dissolved solutes, such as sugars or mineral ions, whereas osmosis involves the transport of water only                                                  - in diffusion + osmosis, substances move down a concentration gradient whereas in active transport they move against in 

what’s the difference between osmosis + diffusion + active transport

the things that carry the genes that contain instructions for making both new cells and the tissues + organs - each chromosome carry a large numbe of genes 

- able to differentiate into almost any type of cells - can help in medical treatment - can divide very quickly + grow 

- some people question the use of potential human beings as a source of cells                                 - therapy using them can be slow, difficult, expensive and hard to control                                       - not as many to use 

regrow limbs, paralysis, Parkinson’s, diabetes, therapeutic cloning, coeliac disease 

uses for stem cells in medical treatment 

cells that have not undergone differentiation and are therefore unspecialised 

breathing: when you take a breathe + recharge the air in our lungs, the concentration of oxygen in your blood is lower than the concentration of oxygen in your lungs                             - oxygen diffuses into your blood due to the concentration gradient                                            - the opposite is happening with carbon dioxide: it is higher in the blood than in the air in your lungs so CO2 diffuses out of the lungs 

examples of diffusion in living organisms 

cell membrane, cytoplasm, nucleus, mitochondria, ribosomes 

what are the sub cellular structures in animal + plant cells 

its structure is permeable to some substances but not to others. It therefore controls the movement of substances in and out of the cell

what’s the function of the cell membrane 

gel-like substance where chemical reactions take place

contains the genetic material, including DNA, which controls the cells activities 

organelles that contain the enzymes for respiration, and where most energy is released in respiration

what’s the function of the mitochondria 

tiny structures where protein synthesis occurs

active transport moves substances from a more dilute solution to a more concentrated solution (against the concentration gradient) which requires energy from respiration 

cells which have a nucleus to store DNA + genetic information 

cells that dont have a nucleus to store DNA so is free floating in the cytoplasm 

- process by which cells become specialised for a particular function                                          - when cells express specific genes that characterise a certain type of cell, we say it has become differentiated 

a cell that has gone through cell differentiation and become a cell that has a specific function 

sub-cellular structures which allow it to carry out a certain function

what do cells aquire during cell differentiation 

it is an essential process for the development, growth, reproduction of all multicellular organisms 

eyepiece lens magnifcation x objective lens magnifictaion 

how do you calculate magnification of a microscope 

how do you calculate the magnification of an image 

number of times bigger the image is compared to the real object 

use the known size of the cell + work out how many times the sub-cellular structure fits in the cell

how do you judge the relative size / area of sub-cellular structures 

particles moving in - particles moving out 

- large surface area.                                                                                                                              - thin membrane to provide a short diffusion path.                                                                             - (in animals) having efficient blood supply                                                                                            - (in animals, for gaseous exchange) being ventilated 

how is the effectiveness of an exchange surface increased 

1)plants cell: e.g. onion cells - peel off a thin layer of tissue using forceps, place on water drops on slide. animal cell: e.g. cheek cells - swab inside of cheek with cotton bud , smear onto the centre of the slide. 2)add a drop of stain with a pipette. 3)lower coverslip at angle without trapping air bubbles

describe how to prepare a microscope slide 

do animal cells have a permanent vacuole 

do bacteria cells have a permanent vacuole 

cell wall, chloroplasts, permanent vacuole 

what additional sub-cellular structures are there in plant cells that aren’t in animal cells

contain chlorophyll -> to absorb light for photosynthesis to make glucose 

what’s the function of the chloroplast 

filled with cell sap -> help to keep cell turgid / support plant

what’s the function of the permanent vacuole 

thickness of diffusion surface, difference in concentrations, temperature, available surface area 

if it is smaller, diffusion occurs quicker as particles have less distance ot travel

how does the thickness of diffusion surface affect the rate of diffusion

called to concentration gradient - the bigger the difference, the steeper the gradient + the faster the rate of diffusion 

how does difference in concentration affect rate of diffusion 

particles move around more quickly so diffusion takes place more rapidly as random movement of the particles speed up

how does temperature affect the rate of diffusion 

if the area that diffusion can take place increases, the rate of diffusion also increases as more substance can move in a given time 

how does available surface area affect rate of diffusion 

get rid of ethical issues, easier to access, can be used in cloning 

patient will have to take immunosuppressants if the stem cells aren’t their own, could get infected, can’t differentiate into as many different type of cells as embryonic 

what are the two types of stem cells in humans 

embryonic stem cells can diffrentiate into many cell types whereas adult stem cells can only differentiate into certain type of cell e.g. bone marrow stem cells cn only differentiate into blood cells

what is the difference between embryonic stem cells and adult stem cells

an embryo is produced with the same genes as the patient - stem cells aren’t rejected from the patients body + so many can be used for medical treatment 

plant stem cells can differentiate into many more cell types than animal stem cells throughout their whole life

how are plant stem cells different to animal stem cells

people dont like the idea of cloning, ‘playing god’, can the embryo consent?, when is the embryo ‘alive’?

what are some of the social + ethical issues relating to the use of stem cells

in school + college lavatories, what is the maximum temperature cultures should be incubated at 

more resolution + more magnification which means people can study cells in finer detail which have allowed people to understand more sub-cellular structures

cumbersome, black + white images, can only view dead samples 

easier to carry, colour images, can view live samples

eukaryotic: have mitochondria, have a nucleus, large, slow growth rate, simple cell wall prokaryotic: faster growing rate, no nucleus, small, DNA arranged in loop in the cytoplasm, complex cell wall

compare prokaryotic cells + eukaryotic cells 

by acquiring different sub-cellular structures

how do multi-cellular organism cells differentiate to form specialised cells 

- allows mineral ions to be absorbed into plant root hairs from very dilute solutions in the soil -> plants require ions for health growth.                                                                                                    - allows sugar molecules to be absorbed from owe concentrations in the gut into the blood which has a higher concentration -> sugar molecules are used for cell respiration 

animal cells diffrentiate at an early stage whereas plant cells retain the ability to specialise throughout their whole life 

how do animal + plant cells differentiate differently 

the ability to distinguish between two objects -> the higher the resolution, the more clear the difference 

the diffusion of water from a dilute solution to a concentrated solution across a partially permeable membrane 

interphase: cell browns bigger, increase their mass + carry out normal cell activities. they replicate ther DNA to form two copies of the same chromosomes ready for cell division 

mitosis: the process where one set of chromosomes is pulled to each end of the dividing cell + the nucleus divides 

cytokinesis: stage during which the cytoplasm + the cell membranes all divide to form 2 identical daughter cells 

- RBC has no nucleus, PC does / both have cytoplasm + cell membrane / RBC has no cell wall, PC does / RBC doesn’t contain chloroplast or chlorphyll, PC does / RBC has no permanent vacuole, PC does / RBC contains haemaglobin, PC does 

compare the structure of red blood cells with the structure of plant cells (6 marks)

1) clip slide onto stage + turn on light. 2) select lowest power objective lens. 3) a. use coarse focus dial to move stage closer to the lens. b. turn coarse focus dial to move stage away from lens until image comes into focus. 4) adjunct fine focusing dial to get clear image. 5) swap to higher power objective lens, then refocus 

describe how to use a microscope to view cells 

examples of specialised cells in animals 

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